Wall structures formed from a plurality of interconnected, prefabricated, portable panels are used extensively in commercial and industrial buildings for dividing interior regions into smaller work regions. Such structures have proven particularly effective in providing greater privacy within the building, and at the same time improving the interior appearance. For this purpose, the panels are provided with many different exterior finishes, such as colored plastics, carpets and fabrics. Some of these panels also tend to minimize noise, particularly when they are provided with soft exterior finishes, such as by being covered by carpeting or fabric. Many panels of this type are also provided with slotted rails extending vertically along the edges thereof, whereby fixtures such as desks, shelves, filing cabinets and the like can be mounted on the panels. Due to the desire to mount these fixtures on the panels, the panels must thus be provided with substantial strength and, accordingly, are normally provided with a relatively strong and rigid core so as to provide the necessary strength.
While panels of the above type tend to minimize noise, nevertheless any noise absorption capability of the panel is normally provided solely by the outer coverings. Further, since these panels are normally of a height substantially less than the floor-to-ceiling height, this also permits the transmission of substantial noise over the panel which, when coupled with the inability of the panels to absorb a high percentage of sound at various frequencies, thus results in these panels being unacceptable for use in situations where a high noise reduction and absorption by the panel is necessary. Because of this inability to absorb a high percentage of the sound in the environment, these panels have conventionally been referred to as a nonacoustical-type panels.
In recognition of this problem, U.S. Pat. Nos. 4,084,366, 4,084,367 and 4,155,211, which are owned by the assignee of this invention, disclose acoustical panels which represent a substantial improvement over prior structures in terms of their ability to absorb a high percentage of various frequency sound waves while at the same time being both aesthetically pleasing in appearance and structurally strong so as to permit accessories and fixtures to be hung thereon. In the panels disclosed in the above-mentioned patents, the core of the panel is provided with a honeycomb structure which is covered by perforated side skins to form a plurality of Helmholtz resonators for effectively absorbing sound waves, particularly those sound waves of lower frequency. The side skins in turn are covered by layers of porous sound-absorbing material, such as fiberglass, to effectively absorb those sound waves of higher frequency, whereby the resultant panel possesses a capability of absorbing a significant percentage of sound wave frequencies typically encountered within an office-type working environment.
While the panels disclose in the above-mentioned patents have proven desirable for use in an office-type environment, and have also been effective for absorbing at least a significant part of sound waves of selected frequencies, nevertheless substantial additional research and development has been carried out on acoustical panels of this type in an attempt to further improve upon the sound-absorbing characteristics thereof so as to provide the panel with a high and consistently reproducible noise-reduction coefficient (NRC). More specifically, this additional research and development has been carried out with respect to improving the sound-absorbing capability of the fiberglass layer such that this latter layer will be more effective for absorbing a greater percentage of the existing sound waves and a greater percentage of different frequency sound waves as typically encountered in the office environment. At the same time, it has been essential that this development with respect to the fiberglass layer still result in the side of the panel having a soft touch or feel as provided by the fiberglass layer and the external fabric covering thereover, with such soft layer being such as to provide a very pleasing appearance when covered.
Accordingly, it is an object of the present invention to provide an improved acoustical panel for absorbing a large degree of directed sound of various frequencies, which panel possesses a high noise reduction coefficient and also possesses substantial strength to enable fixtures to be hung thereon.
More specifically it is an object of this invention to provide an improved acoustical panel, as aforesaid, which possesses an improved fiberglass sound-absorbing layer which is of variable density so as to provide highly improved sound-absorbing capability over a significant range of frequencies, while at the same time providing an extremely soft top surface so as to enhance or maintain the desirable aesthetic and touch properties deemed essential for the panel sidewalls.
In the improved acoustical panel as aforesaid, a variable-density fiberglass layer is preferably provided with a very low density on the outer or top surface thereof, which low density extends over a significant depth so as to provide the desired soft surface, with the remaining thickness of the fiberglass layer being of significantly increasing density so that the fiberglass layer, over a majority of the thickness thereof, has a density variation in the range of at least about 3 to 1 as measured between the outer and inner surfaces The rear or inner surface of the fiberglass layer has bonded thereto a thin extremely high-density mat of fiberglass material having a density which is a large multiple (such as ten times) that of the soft outer surface This high density mat in turn overlies the skin of the panel, whereby the overall acoustical panel provides a highly improved capability of absorbing substantial quantities of sound waves of significantly different frequencies, and thereby provides the panel with a desirably high noise reduction coefficient.
Other objects and purposes of the invention will be apparent to persons familiar with panels of this general type upon reading the following specification and inspecting the accompanying drawings.